Is there any author that argues for radical moral pluralism?

Question

Let me first clarify what I mean with "radical" here. While many modern authors, if not all, accept moral pluralism of sorts, all that I know of express either the hope, if not the conviction, that there is some sort of baseline agreement or common structure, or even argue for the possibility of them, despite the arguments given by themselves against such possibility earlier.

Thus, in general, there seems to be the overall picture that even though there are good arguments for a general moral pluralism (Nagel's View from Nowhere, other prominent ones see below), there seems to be no author that is fully committed to the idea that there can be humans (pathopsychology excluded) that do not share at least some moral sentiments/structures/principles/values/etc.

Examples

This section is mainly to show what kind of arguments and discourse I am fully aware of and where I am coming from, i.e. to give further context.

Simon Hope writes in his paper Hope, Simon (2011): 'Common humanity as a justification for human rights claims', in: G. Ernst and J.-C. Heilinger (eds.), The philosophy of human rights: Contemporary controversies. Berlin: De Gruyter, pp. 211-230. the following about Walzer, Nussbaum, and Davidson:

Nussbaum and Michael Walzer have offered arguments on this score: in order for us to recognize different ethical outlooks at all, there must be a common substantive set of “moral facts” that are “immediately available to our understanding”, against which moral disagreement is intelligible (Walzer 1987, 23 – 29; cf. Nussbaum 1993, 242 – 269). If this view is plausible, we cannot deny the existence of a common ‘framework’, as Walzer puts it, of moral intuitions that are only fully substantiated in historically contingent cultural ways of going on.

This line of argument appears to have good Davidsonian roots. Davidson’s basic point – that “the more basic a norm is to our making sense of an agent, the less content we can give to the idea that we disagree with respect to the norm” (Davidson 2004, 50) – is surely correct. One might then conclude that some values must be shared if we are to identify moral disagreements at all. (Hope: 217)

But he goes on to dispell the hopes for such a framework on the following pages, evenly with the tries of Griffin to argue for autonomy, liberty, and minimal provision as minimal shared values and more common sense arguments as put forward by e.g. Tasioulas.

But still, he offers an alternative to intuitionists and welfarist tries to justify shared values that should universally be protected by human rights in the form of "preserving effective action":

I take effective action to be determined by both a set of basic human needs, which we cannot help but have, and a degree of influence over the shape of the social institutions and conventions under which action to meet these needs must occur. (Hope: 224)

Similarly, Stephen Angle in his Angle, Stephen C. (2002): Human rights and Chinese thought: A cross-cultural inquiry. Cambridge: Cambridge University Press, pp. 5-11 accepts arguments of MacIntyre and Rorty for moral pluralism, but points out (similar to Bell, D. A. (2000). East meets West: human rights and democracy in East Asia. Princeton University Press.) that no Eastern regime or individual leader has ever openly argued for torture, murder, or rape being right, just for some rights being temporarily disposable for the greater good (with ample historical sources) and thus assume an interculturally shared moral base, albeit acknowledging the lack of moral absolutism in "the East".

Furthermore, the rising star of Moral Foundations Theory gives a rising number of empirical data and helps establishing a common, empirically validated, structural network, see Graham, Jesse, et al. (2013): 'Moral Foundations Theory: The Pragmatic Validity of Moral Pluralism', in: P. Devine and A. Plant (eds.), Advances in Experimental Social Psychology, vol. 47. Burlington: Elsevier Science, pp. 55-130.

Thus, even if also the empirical evidence for moral pluralism is overwhelming, so is the empirical evidence for objectivism and meta-ethical structures allowing for that very pluralism, see Wright, Jennifer C., Grandjean, Piper T. & McWhite, Cullen B. (2013): 'The meta-ethical grounding of our moral beliefs: Evidence for meta-ethical pluralism', Philosophical Psychology 26:3, pp. 336-361.

Therefore, the question remains:

Are there any writers that argue for radical moral pluralism in the sense that not a single moral value or structure is shared, i.e. utter and complete incommensurability? And if not, which author may be or is considered as coming closest to that?

Remarks/Requirements

1. Please try to give a sourced answer, ideally with quotes and a short explanation.
2. Even more interesting would be if a text would argue along these lines by denying a common human nature as having any normative implications and not only the possibility but also the reality of radical moral pluralism, as this is where the research is aiming at.
3. Authors including empirical studies are most welcome as well.

Answer 1

I will offer suggestions for direction to explore, rather than sources.

As one poster noted, Nietzsche sounds like a good candidate for what you are looking for. He held that those of powerful will were not constrained by social morality, which is pretty much "radical moral pluralism". And it is not Nietzsche alone, but most of the Existentialist movement who held that value was individually and personally created -- which would include moral values. So -- look in the moral writings of the existentialists.

A second possible source is theistic apologetics, specifically looking among those apologists who hold by Divine Command Theory. Under DCT, there is no moral reference other than the command of a deity. So under DCT, most of your presuppositions above are rejected, there would be no "common substantive set of “moral facts”", no "autonomy, liberty, and minimal provision as minimal shared values", and DCT advocates WILL "openly argue[d] for torture, murder, or rape being right" IF a God commands them!

Another area of thinkers to look would be among the more thoroughly reductive materialists. IF there is only matter, then it is difficult to ascribe anything but delusional or confusion designation to values, and morality. Emergentist materialists can arrive at morality through emergent social norms, etc, but the reductionists do not have this option. I have encountered a lot of materialists in online discourse who have followed this thinking to its logical conclusion, and deny there is any such thing as morality. These anti-moralists I have had discourse with agreed that evolution had bequeathed us some patterns of behavior and channels of thought which produced the false belief in morality, but WHAT evolution gifted us with -- was just what was evolutionary advantageous to us, plus some random accidents. IE valuing kin, and tribe, and species, and sense of ownership of possessions, sexual loyalty/jealousy, anger and thirst for revenge, etc are all bioadvantages that we RATIONALIZE as morality, and get tied to all sorts of other social bs. This is not exactly what you asked for, but it is awfully close. I presume there are published authors who argue these points as well.